A Danish company has moved to prevent one of its drugs being used to execute prisoners in the US.

Lundbeck will demand that US distributors sign an agreement stating that they will not make pentobarbital, which is a sedative with a wide range of uses, available for prisons using it for lethal injections.

"Lundbeck will have to approve each order and everyone buying the product must sign a paper stating they will not sell it on to prisons," said Ulf Wiinberg, chief executive of Lundbeck.

He said US prisons had been able to buy the drug indirectly through stores and wholesalers. "We are confident that our new distribution programme will play a substantial role in restricting prisons' access," he said, promising to take action against any distributor selling the drug to a prison.

Pentobarbital has been used to execute prisoners in Georgia, Alabama, Ohio and Oklahoma. The drug, which is produced by Lundbeck's plant in Kansas, is used in the treatment of epileptic seizures, but has also become a key element in US executions.

Wiinberg said the company discussed the issue with its shareholders and human rights organisations. "I have not experienced any pressure from our shareholders," he said. "My understanding is that they have felt that we did the right thing."

In April the UK business secretary, Vince Cable, announced a ban on the export to the US of three pharmaceutical drugs used to execute prisoners on death row, including pentobarbital. The move came after a parliamentary inquiry heard that enough pharmaceutical drugs had been sold to the US by licensed British wholesalers since last summer to execute 100 death row inmates.

Reprieve, the London-based rights group that sought the ban, welcomed the news. "Lundbeck has proven that manufacturers can control the use and distribution of their drugs. Any company manufacturing execution drugs who refuses to take such steps will be directly complicit in executions," Reprieve investigator Maya Foa said in a statement. "Other pharmaceutical companies should now follow Lundbeck's example."